I assume this lens is for street photography, is that right? Can I ask someone that does use this type of lens, why is f1.4 required? I do landscapes and clearly don't need this lens and the 1.4 comes at a huge premium so I like to understand the drivers.

This seems to be very interesting lens indeed. How come this lens is superior to 35mm from Canon, Nikon, Sony, and Zeiss ??

Because it´s newer technology with new design..

Sigma has really been on a roll since they released the 85mm f/1.4 HSM a few years ago. The 120-300 2.8 OS is a fantastic piece of equipment for the price. I am so waiting for the leaked 300mm f/2.8 OS prime

Let's see if this changes the water on the beans. Here's hoping. The 50 1.4, and the 20, 24, and 28 1.8s got mixed reviews at best over the last couple years, so I never considered any of them. If Sigma is turning a corner that's great news: I remain very happy with my 8-16mm on D90 but I can't count the number of souls who say I just lucked into a good copy.

I'm told the 120-300 2.8 is a great lens too and that would likely be a more useful range for me than a 70-200.

That has posted some spectacular results! That may have to go on a wish list!

I have read that Sigma has implemented a new Quality Assurance (With the Merrill name) that checks their "Pro" line before they leave the shop. They say it is suppose to reduce the calibration (front/back focus) issues substantially. I hope this does help - I would like to take chances on their lenses.

This seems to be very interesting lens indeed. How come this lens is superior to 35mm from Canon, Nikon, Sony, and Zeiss ??

".......Let's start with the optics. It's remarkably sharp, even wide open, outperforming not only its Canon, Nikon and Sony equivalents, but also the far more expensive Carl Zeiss Distagon T* 1,4/35 in lab tests. Chromatic aberration is also impressively well controlled (both lateral and longitudinal), distortion is low and vignetting more-or-less typical for its class. The rendition of out-of-focus regions is generally quite attractive, although complex backgrounds can end up looking rather 'fussy'. The overall result, though, is a lens that delivers fine-looking images with the minimum of fuss, shot after shot....."